Add last updated date and make publish&change dates show only when necessary

templates/page.html

@@ -1,7 +1,12 @@
 {% extends "base.html" %} {% block content %}
     <h3>{{ page.title }}</h3>
     <article>
+        {% if page.date and page.date is defined %}
         <p>Published on: {{ page.date }}</p>
+        {% endif %}
+        {% if page.updated and page.updated != page.date %}
+        <p>Last updated on: {{ page.updated }}</p>
+        {% endif %}
         <div>
             {{ page.content | safe }}
         </div>